1. Technical Field of the Invention
The present invention relates to a recording apparatus for recording information signals on a recording medium and to a recording medium on which information signals are recorded.
2. Prior Art
Conventionally, there is provided an optical disk having a wobble for a boundary between a land and a groove formed as a recording track on a signal recording surface. There is also provided a recording apparatus in compliance with such an optical disk.
The recording apparatus tracks a recording optical beam along a slightly wobbling groove on the optical disk such as a music MD or a CD-R disk for computers.
In addition, the recording apparatus uses a frequency filter to electrically separate a wobbling frequency component from a tracking guidance signal. The recording apparatus gradually multiplies this wobbling frequency component to use it as a synchronization clock for recording data.
When there are two disk formats with different wobbling frequencies, it is necessary to provide a separate disk specific to each wobbling frequency. There has been a need to manufacture two types of blank disks for marketing. This is also inconvenient for users. A recording apparatus compatible with each disk type is also required.
The present invention has been made in consideration of the foregoing. It is therefore an object of the present invention to provide a recording medium available for an apparatus which complies with two disk formats having different wobbling frequencies. It is also an object of the present invention to provide a recording apparatus which records data with high quality on such a recording medium.
For solving the above-mentioned problems, a recording apparatus according to the present invention forms a land and a groove as a recording track on a signal recording surface of a disk-shaped recording medium. Data is recorded on a disk-shaped recording medium provided with a wobble between the land and the groove. The wobble has a waveform which is a combination of waveforms with first and second frequencies. The second frequency is lower than the first frequency.
The recording apparatus comprises: drive means for rotatively driving the recording medium; light irradiation means for condensing a laser beam and irradiating it onto a target track and both tracks adjacent thereto on a signal recording surface of the recording medium which is rotatively driven by the drive means; light detection means for detecting a return light from each of the target track and both tracks adjacent thereto and converting the return light into an electric signal; high-pass filtering means for filtering a high-frequency component in a signal corresponding to the return light which is returned from the target track and is output from the light detection means; low-pass filtering means for filtering a low-frequency component in a signal corresponding to the return light which is returned from each of both tracks adjacent to the target track and is output from the light detection means; arithmetic means for computing a signal which passed the high-pass filtering means and a signal which passed the low-pass filtering means; and means for generating a reference signal based on a phase of the signal computed in the arithmetic means. The arithmetic means nullifies a nonlinear component due to wobbling of both tracks adjacent to the target track and extracts only a waveform component from the first frequency.
There are formed a land and a groove as a recording track on a signal recording surface of a recording medium according to the present invention. The disk-shaped recording medium is provided with a wobble between the land and the groove. The wobble has a waveform which is a combination of waveforms with first and second frequencies. The second frequency differs from the first frequency.
A wobble is formed on a recording track of the recording medium according to the present invention so that the first frequency and the second frequency waveforms are superposed on each other. It is impossible to use a recording apparatus which is compatible with the first frequency or the second frequency.
The recording apparatus using a first high-pass frequency wobble separates a wobbling frequency component in the wobble from a tracking error signal. The recording apparatus then suppresses a wobbling frequency component of the second low-pass frequency to generate a high-quality recording synchronization clock. This provides recording quality equivalent to that available with a single frequency wobble.
As mentioned above, the present invention extracts a high-pass component from the wobble which is formed on the recording medium""s recording track and comprises the superposed frequencies with high-pass and low-pass components. The present invention nullifies a nonlinear component, especially a cross modulation component from the adjacent wobble. Namely, the present invention removes not only low-pass components mixedly reproduced from the target track due to wobbling, but also cross modulations which are not removed by a filter and are caused by adjacent track""s wobbling.
According to the present invention, a reference signal used as a time reference for recording data is a pure high-pass component in the target track wobble. As a result, an optical disk records a series of high-quality data with little fluctuation in a time axis.